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How Denarau Handles Waste

One of the great challenges in building a large resort has been to design, construct and maintain a waste water reticulation system. With the new strict standards that are being
26 Aug 2017 11:00
How Denarau Handles Waste
Aerial of Denarau Island.

One of the great challenges in building a large resort has been to design, construct and maintain a waste water reticulation system. With the new strict standards that are being introduced in various forms all over the world because of the greater understanding of the interconnection between all the elements that can be impacted by Climate Change the challenge has increased significantly.

The importance of finding the best answer to the issues that are created by the need to control and dispose of the waste in a tourism development in such a way that the environment, the very reason the people come to a certain destination, is preserved in the best possible condition is now a real focus for many of the operators in Fiji.

While the challenges on the mainland are somewhat easier to handle than in an island resort in the more remote parts of Fiji, they remain basically the same.

Simply put, the objective is to create a system that disposes of human waste and the associated fluids in such a way that minimum damage is done to the environment. Specifically, we are talking about human body waste, but it is never captured, transported or treated alone, but always contains pollutants from a number of different sources.

 

Generally, human waste will only be around fifteen percent of the total fluids to be handled.

The mass will typically include water from showers, washing machines (including the often damaging residue of the cleaning products added to the clothes washing function to improve efficiency), dish washing sinks including small particles of food material, cooking oils, fats and detergents. This is a potentially damaging and unpleasant mix.

Along the way, in the transportation process, there are many areas where spills, unintended release or deliberate disposal can occur. It is in the transport process of the fluid/solids mixture from the source (toilet, washing or waste water) to the planned disposal facility that issues arise.

To understand the challenges and the technology that makes for an efficient and acceptable disposal system, a look at one of the best in Fiji is helpful.

 

The benchmark in the tourism industry here is the Denarau system.

Remember, the objective is to transport the fluid mass from the origin place to the disposal area without any accidental or unplanned release on the way.

So in Denarau the system needs to collect the waste from sources spread over the whole seven hundred or so acres and move it in a controlled fashion aver an average of four kilometres to the government treatment facility at Navakai., where it is handed over for treatment along with waste from many other areas of Nadi.

The actual treatment is not part of the task for the operators of the reticulation system for Denarau, Denarau Corporation Limited; with waste their task is to deliver it to the treatment plant. How does this happen.

 

Three objectives for the system

There are three main objectives for the system and each has to be performed correctly if the system is to be regarded as working correctly.

The first is that the waste must be immediately collected and removed from the source, the locations in the house or resort such as toilets, laundries and sinks where the waste is created.

Secondly, it has to be absolutely contained within the reticulation system with no risk of overflow or backup, a task made difficult because there are quite significant peaks where almost every home is releasing waste into the system at the same time during the morning and early night.

Thirdly it has to be transported from the Denarau collection sites to a central pumping station and then delivered to the Navakai Treatment Facility where solids are removed through screening and settlement and the remaining fluids chemically treated to destroy bacteria. This collection and transportation process is quite complex.

Because the land that comprises Denarau is basically flat it is necessary to move the waste to the main collection well by pumping it through a network of pipes. In other locations, where there is a fall in the land, the waste can be moved by gravity with the liquids carrying the solids and surprisingly small falls are required to achieve the movement.

One of the greatest sewer mains in the world, the London system has worked perfectly for over a hundred and fifty years with a fall of only several inches every mile.

However, because of lack of fall, the Denarau system has a series of twenty three pumping stations which service the residential precincts, Industrial area,

Marina, Shopping Centre and relay from the Resorts and each pumping station has a storage well in which the pump is immersed.

Each well has a cover at the top for inspections so that and blockages in the pipes can be cleared easily and each pumping well has a hatch that allows for the pump to be lifted out for maintenance and repair and there is normally a second pump that takes over if there is a problem with the operating pump.

 

The pumps operate using electricity and the main pumping station is connected to a backup generator system.

Each pumping station is fitted with a warning light that flashes if there is a mechanical or electrical failure so that immediate action can be taken to restore the reticulation process.

Over time there will be a build-up of solids in the bottom of the wells and these are regularly cleared using a sucker truck so that maximum storage space is available.

Under normal conditions, storage is capable of holding stored waste up to 24 hours.

With the current environmental standards set by government for the handling of waste in the tourism sector, a significant amount of capital needs to be committed to the systems, but the important thing is to ensure that the original design is capable of providing the standards and that planned maintenance ensures that the system functions without any issues.

John Ross is  a Nadi-based marketing and advertising specialist with a long background in tourism. For feedback on this article, please email him: johnrossfiji@gmail.com

 

 



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